From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 633B7C433F5 for ; Thu, 26 May 2022 09:50:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9C6AA8D0003; Thu, 26 May 2022 05:50:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 972848D0001; Thu, 26 May 2022 05:50:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8385A8D0003; Thu, 26 May 2022 05:50:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 70F668D0001 for ; Thu, 26 May 2022 05:50:35 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 41C9180280 for ; Thu, 26 May 2022 09:50:35 +0000 (UTC) X-FDA: 79507424430.01.E0CF81B Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf16.hostedemail.com (Postfix) with ESMTP id E4D3418000C for ; Thu, 26 May 2022 09:50:19 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 665981474; Thu, 26 May 2022 02:50:33 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.2.68]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 28ACF3F73D; Thu, 26 May 2022 02:50:27 -0700 (PDT) Date: Thu, 26 May 2022 10:50:23 +0100 From: Mark Rutland To: Tong Tiangen Cc: James Morse , Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Robin Murphy , Dave Hansen , Catalin Marinas , Will Deacon , Alexander Viro , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , x86@kernel.org, "H . Peter Anvin" , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Kefeng Wang , Xie XiuQi , Guohanjun Subject: Re: [PATCH -next v4 3/7] arm64: add support for machine check error safe Message-ID: References: <20220420030418.3189040-1-tongtiangen@huawei.com> <20220420030418.3189040-4-tongtiangen@huawei.com> <46e5954c-a9a8-f4a8-07cc-de42e2753051@huawei.com> <87bdb1c6-5803-d9c0-9208-432027ae1d8b@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87bdb1c6-5803-d9c0-9208-432027ae1d8b@huawei.com> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: E4D3418000C X-Stat-Signature: ojf6eitd1w5p4oak9jfs4xshkkqzfdto Authentication-Results: imf16.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf16.hostedemail.com: domain of mark.rutland@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=mark.rutland@arm.com X-Rspam-User: X-HE-Tag: 1653558619-509056 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, May 26, 2022 at 11:36:41AM +0800, Tong Tiangen wrote: > > > 在 2022/5/25 16:30, Mark Rutland 写道: > > On Thu, May 19, 2022 at 02:29:54PM +0800, Tong Tiangen wrote: > > > > > > > > > 在 2022/5/13 23:26, Mark Rutland 写道: > > > > On Wed, Apr 20, 2022 at 03:04:14AM +0000, Tong Tiangen wrote: > > > > > During the processing of arm64 kernel hardware memory errors(do_sea()), if > > > > > the errors is consumed in the kernel, the current processing is panic. > > > > > However, it is not optimal. > > > > > > > > > > Take uaccess for example, if the uaccess operation fails due to memory > > > > > error, only the user process will be affected, kill the user process > > > > > and isolate the user page with hardware memory errors is a better choice. > > > > > > > > Conceptually, I'm fine with the idea of constraining what we do for a > > > > true uaccess, but I don't like the implementation of this at all, and I > > > > think we first need to clean up the arm64 extable usage to clearly > > > > distinguish a uaccess from another access. > > > > > > OK,using EX_TYPE_UACCESS and this extable type could be recover, this is > > > more reasonable. > > > > Great. > > > > > For EX_TYPE_UACCESS_ERR_ZERO, today we use it for kernel accesses in a > > > couple of cases, such as > > > get_user/futex/__user_cache_maint()/__user_swpX_asm(), > > > > Those are all user accesses. > > > > However, __get_kernel_nofault() and __put_kernel_nofault() use > > EX_TYPE_UACCESS_ERR_ZERO by way of __{get,put}_mem_asm(), so we'd need to > > refactor that code to split the user/kernel cases higher up the callchain. > > > > > your suggestion is: > > > get_user continues to use EX_TYPE_UACCESS_ERR_ZERO and the other cases use > > > new type EX_TYPE_FIXUP_ERR_ZERO? > > > > Yes, that's the rough shape. We could make the latter EX_TYPE_KACCESS_ERR_ZERO > > to be clearly analogous to EX_TYPE_UACCESS_ERR_ZERO, and with that I susepct we > > could remove EX_TYPE_FIXUP. > > > > Thanks, > > Mark. > According to your suggestion, i think the definition is like this: > > #define EX_TYPE_NONE 0 > #define EX_TYPE_FIXUP 1 --> delete > #define EX_TYPE_BPF 2 > #define EX_TYPE_UACCESS_ERR_ZERO 3 > #define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4 > #define EX_TYPE_UACCESS xx --> add > #define EX_TYPE_KACCESS_ERR_ZERO xx --> add > [The value defined by the macro here is temporary] Almost; you don't need to add EX_TYPE_UACCESS here, as you can use EX_TYPE_UACCESS_ERR_ZERO for that. We already have: | #define _ASM_EXTABLE_UACCESS_ERR(insn, fixup, err) \ | _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, wzr) ... and we can add: | #define _ASM_EXTABLE_UACCESS(insn, fixup) \ | _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, wzr, wzr) ... and maybe we should use 'xzr' rather than 'wzr' for clarity. > There are two points to modify: > > 1、_get_kernel_nofault() and __put_kernel_nofault() using > EX_TYPE_KACCESS_ERR_ZERO, Other positions using EX_TYPE_UACCESS_ERR_ZERO > keep unchanged. That sounds right to me. This will require refactoring __raw_{get,put}_mem() and __{get,put}_mem_asm(). > 2、delete EX_TYPE_FIXUP. > > There is no doubt about others. As for EX_TYPE_FIXUP, I think it needs to be > retained, _cond_extable(EX_TYPE_FIXUP) is still in use in assembler.h. We use _cond_extable for cache maintenance uaccesses, so those should be moved over to to EX_TYPE_UACCESS_ERR_ZERO. We can rename _cond_extable to _cond_uaccess_extable for clarity. That will require restructuring asm-extable.h a bit. If that turns out to be painful I'm happy to take a look. Thanks, Mark.